This collection contains large size versions of Conformer-CTC (around 120M parameters) trained on Mozilla Common Voice 10.0 (Russian), Golos (Russian), Russian LibriSpeech (RuLS) and SOVA (RuAudiobooksDevices, RuDevices) datasets with around 1636 hours of Russian speech.
It utilizes a Google SentencePiece  tokenizer with vocabulary size 128, and transcribes speech in lowercase russian alphabet along with spaces.
Conformer-CTC model is a non-autoregressive variant of Conformer model  for Automatic Speech Recognition which uses CTC loss/decoding instead of Transducer. You may find more info on the detail of this model here: Conformer-CTC Model.
All the models in this collection are trained on a composite dataset (NeMo ASRSET) comprising of more than a thousand hours of Russian speech:
The tokenizer for this model was built using text corpus provided with the train dataset.
We build a Google Sentencepiece Tokenizer  with the following script :
python [NEMO_GIT_FOLDER]/scripts/tokenizers/process_asr_text_tokenizer.py \ --manifest="train_manifest.json" \ --data_root="<OUTPUT DIRECTORY FOR TOKENIZER>" \ --vocab_size=128 \ --tokenizer="spe" \ --spe_type="unigram" \ --spe_character_coverage=1.0 \ --no_lower_case \ --log
The list of the available models in this collection is shown in the following table. The performance of Automatic Speech Recognition models are reported in terms of Word Error Rate (WER%) with greedy decoding. Since this dataset is trained on multiple domains and a much larger corpus, it will generally perform better at transcribing audio in general.
|Version||Tokenizer||Vocabulary Size||MCV 10.0 dev||MCV 10.0 test||GOLOS-crowd test||GOLOS-farfield test||RuLS test||Train Dataset|
|1.13.0||SentencePiece Unigram||128||3.9||4.3||2.8||7.1||13.5||NeMo ASRSET|
The model is available for use in the NeMo toolkit , and can be used as a pre-trained checkpoint for inference or for fine-tuning on another dataset.
import nemo.collections.asr as nemo_asr asr_model = nemo_asr.models.EncDecCTCModelBPE.from_pretrained(model_name="stt_ru_conformer_ctc_large")
python [NEMO_GIT_FOLDER]/examples/asr/transcribe_speech.py \ pretrained_name="stt_ru_conformer_ctc_large" \ audio_dir="<DIRECTORY CONTAINING AUDIO FILES>"
This model accepts 16000 Hz Mono-channel Audio (wav files) as input.
This model provides transcribed speech as a string for a given audio sample.
Since this model was trained on publically available speech datasets, the performance of this model might degrade for speech which includes technical terms, or vernacular that the model has not been trained on. The model might also perform worse for accented speech.